Armatures of prior solenoid-operated hydraulic valves, particularly high pressure valves, were designed as straight cylinders so that the forces necessary to overcome the effects of the hydraulic fluid acting thereon could be achieved. Such designs are often confronted with the need to comply with diverse requirements, such as: they must develop sufficient operating force when the energizing voltage to the solenoid is significantly below its nominal potential; they must operate quickly when de-energized; they must pass fairly large flow rates; and they must be as compact as possible.
The most common way of compliance with a de-energization response requirement is by the incorporation of a return spring. The spring must overcome the collapsing magnetic field and any hydraulic stiction at the instant of de-energization. As a consequence, a stricter de-energization response requirement requires a higher spring force, but a higher spring force either slows the energization response or requires larger armature area for the magnetic flux, and attendant increase in valve size.
The need for the valve to handle a relatively high flow rate typically involves a relatively large valve lift (0.005-0.006 inch stroke for example) and a relatively large sealing area around the valve seat. These too thus require larger diameter armatures and attendant increases in valve size.
An improvement is attained by constructing the armature to a hat-shaped configuration. The brim of the hat is juxtaposed to the stator to allow the area across the non-energized working gap to be larger, but does not increase the nominal diameter of the armature along the crown of the hat. The brim allows the armature to benefit from all magnetic flux fringing that may take place adjacent the fully saturated area of the armature with the result that higher forces can be generated across the working gap. The higher forces enable the armature to comply with larger lift and sealing area requirements that accompany requirements for higher flow rates.
Since the brim of the hat provides a larger working gap area, it becomes feasible for the armature to comprise fluid flow channel structure that reduce the effect of the fluid on the armature. Consequently, the return spring force can be reduced to yield improved energization response.
The foregoing, as well as additional features, advantages, and benefits of the invention, will be seen in the ensuing description and claims, which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.